Submarine-Cable Capacity Has Potential To Double

To lengthen the commercial life of cable in the face of aggressive increases in Internet demand, Soft Decision Forward Error Correction (SD-FEC) has been trialed in concert with a proprietary super channel technology.

In the race to provide increased data capacity for today’s consumers, much of the focus is on wireless solutions like small cells. Yet fiber recently revealed its potential to provide such capacity as well. Infinera has successfully demonstrated a 100-Gb/s optical signal enhanced with Soft Decision Forward Error Correction (SD-FEC)—a technology that could double the transmission capacity of existing submarine cables. That signal was sent across Telstra Global’s dedicated fiber pair within Segment S5 of the AAG cable. Segment S5, which connects San Luis Obispo in Southern California to Hawaii’s island of Oahu, spans 4200 km.

The trial was staged using Infinera’s DTN-X platform and a prototype super-channel line card (see photo). That line card relies on Infinera’s third-generation FlexCoherent processor for real-time SD-FEC processing combined with 500-Gb/s photonic integrated circuits (PICs). With Infinera’s FlexCoherent technology, the line card can be configured for a specific modulation format via simple software controls. By enabling the use of higher-order modulation formats, the SD-FEC allowed Telstra to increase the available capacity on this link. Using the additional error-recovery capability enabled by the SD-FEC, multiple Infinera FlexCoherent modulation formats were able to close the link with no bit errors detected. Such improvements are much needed, as Telstra Global is expecting more than 60% annual growth in its trans-Pacific submarine cable traffic over the next three years.